Recently, hybrid vehicles and electric vehicles have been put into practical use as environment friendly vehicles. In each of such hybrid vehicles or electric vehicles, power needs to be provided to the motor in accordance with load on a motor in order to appropriately drive the vehicle and improve energy efficiency. For example, Japanese Patent Laying-Open No. 2007-89262 (Patent Document 1) discloses a control device allowing for improved fuel efficiency without decreasing travel performance of a vehicle.
The control device disclosed in Japanese Patent Laying-Open No. 2007-89262 controls a vehicle including a step-up converter for stepping up a voltage provided from a direct-current power source and outputting it; and an inverter for converting the direct-current power output from the step-up converter into alternating-current power and outputting it to a vehicular driving motor. The control device appropriately changes a target value for the output voltage of the step-up converter in accordance with a travel mode requested by a driver. When a responsiveness oriented mode is selected, the control device sets as the target value a fixed voltage value higher than a voltage corresponding to an output required by the motor, and controls the step-up converter. On the other hand, when a fuel efficiency oriented mode is selected, the control device sets the target value based on a requested torque for driving the motor, and controls the step-up converter. In this way, the fuel efficiency can be improved without decreasing travel performance of the vehicle.
In the control device disclosed in Japanese Patent Laying-Open No. 2007-89262, when the driver selects the fuel efficiency oriented mode, the output voltage of the step-up converter is controlled to be a value set based on the requested torque for driving the motor. On this occasion, the output voltage of the step-up converter is smaller than that when the response oriented mode is selected. Accordingly, loss can be reduced in the step-up converter. In this way, the travel mode oriented to the travel performance of the vehicle can be employed while improving fuel efficiency.
Patent Document 1: Japanese Patent Laying-Open No. 2007-89262
Patent Document 2: WO 2003/015254